1. Field of the Invention
This invention relates generally to a system and method for the deployment of dual reflectors and, more particularly, to a system and method for the deployment of a side-fed dual reflector system used in connection with a Ka band satellite.
2. Discussion of the Related Art
Various communication systems, such as certain telephone systems, television broadcast systems, internet systems, military communication systems, etc., make use of satellites orbiting the Earth in a geosynchronous orbit, where the satellites are maintained at the same location relative to the Earth or non-geosynchronous orbit, where the satellites do not maintain the same relative position. A satellite uplink communications signal is transmitted to the satellite from one or more ground stations, and then re-transmitted by the satellite to the Earth as a downlink communications signal to cover a desirable reception area depending on the particular use. The uplink and downlink signals are transmitted at a particular frequency bandwidth, such as the Ka frequency bandwidth, and are frequently coded. The satellite is equipped with antenna system(s) including a plurality of antenna feeds that receive the uplink signals and direct the downlink signals to the Earth. The configuration of the antenna feeds and associated antenna optics of the antenna system is designed to provide coverage over a specifically defined area on the Earth, such as the continental United States, although coverage could also be global.
Certain antenna system designs make use of multiple reflectors to direct the downlink signals from the antenna feeds to the Earth, or the uplink signals from the Earth to the antenna feeds. For example, a downlink antenna feed array including a plurality of antenna feeds may be positioned relative to a sub-reflector and main reflector, where the sub-reflector receives the beams from the feeds and directs the beams towards the main reflector to be directed towards the Earth. The orientation of the feed array, sub-reflector and main reflector can take various geometries and configurations depending on a particular design. These designs require that the sub-reflector and main reflector be positioned at select locations and orientations relative to the feed array depending on the focal lengths of the design.
Serious considerations are given to the design of an antenna system of the type discussed herein apart from the actual geometry of the antenna system for providing the desired Earth coverage area. Particularly, the feed array and reflectors need to be mounted on a supporting structure in a manner that minimizes use of the available real estate on the satellite. Further, the antenna system must be compact and lightweight, but be strong enough to survive the satellite launch and space environment, as well as fit within the launch vehicle fairing. Typically, these designs require that the reflectors be at least partially stowed in a folded position during launch, and later deployed once the satellite is in orbit. Known deployment strategies would either deploy each reflector of a dual reflector antenna system on a separate boom or arm, or deploy one of the reflectors on a movable arm and maintain the other reflector fixed to a bus or antenna structure. These designs typically take up significant space to satisfy the launch and deployment requirements. Modern dual reflector antenna systems sometimes have relatively long focal lengths and may require that both reflectors be stowed in a folded position.
What is needed is an improved deployment strategy for deploying multiple reflectors associated with a multiple reflector antenna system. It is therefore an object of the present invention to provide such a strategy.